Ok so I joined the forum a few months back trying to build an underwater camera with a live feed and have use motion eye on a pi for a proof of concept. However the wireless is not powerful enough the transmit through the waterproof housing. there are several videos on YT how to solder a connection for an external antenna but my skills are not that good with solder. Can any one tell me if or how I can connect an external wifi antenna to a Pi Zero.
Cheers Stu
Hi Stuart,
Even with an external antenna you wont be able to get much range with the drone underwater. 2.4GHz is both the frequency that WiFi operates at and waters resonant frequency (microwaves use 2.4GHz and you might even notice your WiFi performance drop when its turned on).
Unfortunately getting an external antenna requires some fine SMD soldering - and an antenna connection at that (The connection should have as low of an impedance as possible (Without getting into it deep, impedance is like resistance but with capacitance and inducance tied in as well))
Hereâs a link to someone thats got it working (its definitely doable with some practice!!)
Hi Stuart
You may get some hints on a forum but you cannot get too much in the way of âskillsâ. Where soldering is involved and you cannot get one on one instruction it is up to you, research and practise. Donât forget the documentation and research bit. It is a waste of time practising bad habits.
But, once you have mastered the âartâ you can sit back and look at a job or project and think âthat looks pretty good, all nice shiny jointsâ. It is pretty gratifying to have confidence that you are very unlikely to have problems down stream due to bad soldering.
Decent tools are a must. You are wasting time with el cheap crappy tools (this applies to almost everything) and you will be only disappointed and disheartened in the long run.
With most coax connectors you mostly only get one chance at it. If you muck it up you generally finish up with a US connector (you might get 2 goes at it) and/or a messy cable end or both. If you have too many goes the cable is probably too short. The modern coax connector is pretty small and most people tend to go for commercially made cables where possible.
Go for it. Soldering is a skill you can use forever.
Cheers Bob
PS.
There is a lot on Tube re this subject. Some of it good but there is a lot you need to take at or less than face value, pretty ordinary and some of it is downright misleading. The problem is to filter out the rubbish and take notice of the useful stuff.
I posted a link to a pretty good Tube some time ago. I will see if I can find it and add it on.
Found it. This is a fair starting point.
Cheers Bob
Cheers for the responses it just seems so small but not impossible. Is there any chance that I could some how use the GPIO pins?
Hi Stuart
For what. What is going out of the antenna connector is RF. That is Radio Frequency. Shock horror, analog!!! I think (am certain) the GPIO pins are logic (what used to be known as up and down DC when the frequencies involved were much slower) so NO unless you mean something else.
Cheers Bob
cheers Bob thatâs the information I was after. I do have a banana Pi zero with rf plug on it but I dont know how to program it. There doesnât seem much support for them.
Donât know anything much about Pis.
Cheers Bob
Hi Stuart,
Sounds like an awesome project!!
We stock a submarine drone that uses a tether to get a signal out of the water, I imagine GLADIUS had a very deep dive into getting some RF signals through water.
Running a serial connection out of the water might be your best bet here.
As Bob mentioned with lots of practice, good tools (good magnification and light are paramount) you can solder it on.
Liam.
Thatâs a great product Liam! That is exactly what I had in mind with the RF cable although my project doesnât require any propulsion, just live feed to a screen. However with no programming or coding experience its tough learning as you go.
Hi Stuart,
How long does the cable have to be? How much room do you have in the enclosure? You can setup the Pi to stream over USB. Hereâs a guide:The Raspberry Pi makes a great USB webcam for $100 | Jeff Geerling
I would prefer wireless connection to tablet. I thought I might be able to run a 3-5m coaxial cable from camera up out of the water and use tablet to view from else where in the boat.
Hi Stuart
If your 5M of cable is carrying video that would be OK. But at 2.4GHz (Wi Fi) you would lose most of your signal in the cable. I donât know what cable would be in use for this sort of thing these days but RG179 was a popular miniature coax and the loss at this frequency would be about 21db which means you would lose 99% of your power in the cable.
I could not find a figure for 2.5GHz, only for 400MHz which is 68.9db per 100 metres or â 3.5db per 5M so used this and normalised for 2.4GHz and this comes out at 21.56db.
Cheers Bob
Edit. 21.56db should be 19db. Still â 99% of power lost.
SuggestionsâŚ
Hi Stuart
Run video and whatever to the surface with your 5M of cable then have a floating container with your WiFi set up with the built in antenna if a plastic container, or if the container is metal a whip type antenna
Will all have to be battery powered of course.
Cheers Bob
PS. That way you would only have a few cm of RF cable.
Cool that was pretty much what I was hopeful of doing⌠Thanks can you recommend a suitable cable and wip.
Stuart.
I havenât done anything involving DIY Wi Fi myself but I would try to get a setup with pre made cable with a connector on to suit your WiFi arrangement. That would save you a lot of grief.
There should be something around with a whip that will mount on a flat surface. Core may have something but as I said I have not had a reason to look for such a device so would not immediately know where to start.
Maybe someone with a bit more hands on savvy might chip in and come up with something.
Before anyone can help though the type of connector you need on the end of the cable must be known.
Cheers Bob
Hey Stu,
Thanks for getting in touch, sorry about the delay in getting back to you. You should be able to put that together using some Coax such as this assuming that you can solder on the connections that youâd need:
Although I agree with Bob, in this case, if you can instead find a prebuilt solution that incorporates the appropriate connections. If you canât find one you can potentially modify a shorter length by extending it with an appropriately rated cable such as the RG-174 Iâve linked (note youâll likely hit attenuation/noise issues when youâve got messy or too many connections between the antenna and transmitter be sure to keep it neat)
If you have an SMA connection on your chosen antenna for example, you can take something like this interface cable and then modify it by splicing the cable on either end to extend it to the length you need. The HAM Radio stack exchange has an excellent discussion on it Iâd suggest taking a read through:
All the best with the project!
Just throwing my 2c in here, Bobâs on the money with signal attenuation. Iâd suggest ditch electronics and go with fibreoptic to the surface, then into a little module to convert to WiFi (Iâd be willing to bet $10 thatâs how the commercial ROVs do it).
Youâll also want to keep your cable density/buoyancy in mind, and making sure your cable is properly waterproof of course (I wouldnât trust ordinary PVC insulation for any great length of time).
Hi Stuart
If you are looking at running video to a floating WiFi unit a shorter version of that cable Bryce linked would be the thing. The SMA connector will mount on a flat sheet and the whip antenna could connect to that. What remains is matching the other connector to your WiFi unit.
The cable is only rated to 1GHz and attenuation figures only seem to be published to that level so if you want to use it make it very short. I would suggest max length 100 to 200mm. At 3M and 2.4GHz I would be very surprised if you got any power at all into an antenna.
I would not recommend this at this frequency, especially with your self confessed lack of soldering skills. and we have already discussed the cons with using a long cable at 2.4GHz. That link re splicing seems to refer to HF, 2 to 30MHz.
By the way. 2.4GHz is not only for microwave ovens but also about the frequency of 10cm Radar where serious power is used. Also the feed to the antenna is waveguide, not coax.
Cheers Bob
And you can get our latest projects and tips straight away by following us on:
